Gas turbine engines comprise a plurality of bladed rotors, each of which comprises a rotor and a plurality of rotor blades mounted on the periphery of the rotor. Each rotor blades has an aerofoil, a platform, a shank and a root. The rotor comprises a plurality of circumferentially spaced axially extending slots. The root of each rotor blade is arranged to locate in a respective one of the axially extending slots in the periphery of the rotor. The roots of the rotor blades are generally fir tree shaped or dovetail shaped and the axially extending slots are correspondingly shaped to receive the roots of the rotor blades.
The bladed rotor arrangement also comprises a plurality of lock plates arranged at a first axial end of the rotor and a plurality of lock plates arranged at a second axial end of the rotor to prevent the rotor blades moving axially relative to the rotor. The lock plates also acts as seals to prevent fluid flowing through the axially extending slots in the rotor and axially between the shanks of the rotor blades and radially between the platforms of the rotor blades and the periphery of the rotor. The radially outer ends of lock plates at the first axial end of the rotor engage grooves defined by radially inwardly extending flanges on the platforms of the rotor blades and the radially outer ends of the lock plates at the second axial end of the rotor engage grooves defined by radially inwardly extending flanges on the platforms of the rotor blades. The radially inner ends of the lock plates engage circumferentially extending grooves in the rotor or circumferentially extending grooves defined by seal plates and the rotor.
However, the arrangement described has suffered from a problem that under certain circumstances, e.g. a combination of manufacturing tolerances of the components, operation of the gas turbine engine for a long period of time at high power conditions, operation of the gas turbine engine for a short period of time at idle conditions followed by shutting down the gas turbine engine, the lock plates may move from their desired position. In particular it has been found that under these circumstances the lock plates may move radially inwardly from their desired positions such that the radially outer ends of the lock plates move out of the groove defined by the platforms of the rotor blades and become wedged against the radially inwardly extending flanges on the platforms of the rotor blades and are at risk of becoming completely disengaged. If the gas turbine engine subsequently operates a slam acceleration manoeuvre the lock plates may chock against the rotor, or seal plates, and additional radial loads may be reacted by the rotor blades through the roots of the rotor blades into the rotor.
Therefore the present disclosure seeks to provide a novel bladed rotor arrangement which reduces or overcomes the above mentioned problem.